To help us choose an air purifier, we gathered 14 of the most popular models at CNET Labs’ product testing facility in Louisville, Kentucky, and put them through the same rigorous testing there. Working with trusted lab colleague Eric Snyder, our goal was to determine which air purifiers offer the best performance in terms of particle removal efficiency, energy consumption, and quietness, while evaluating their respective feature sets and value. Come along as we uncover the science behind the thinking process.
Particle Removal Test
As you probably already know, the air we breathe is more than just air. If you walked outside in the middle of the night and turned on your flashlight, you would witness a universe made of tiny fragments blowing in the wind. What is that thing?
In fact, it is a combination of man-made (human-generated) and naturally occurring particles. The former consists mainly of hydrocarbons, nitrogen oxides and combustion by-products emitted by cities, industry and automobiles, while the latter mainly consists of smoke from forest fires, sulfates, soot and substances from global volcanic activity. We breathe this mixture all the time.
Some of these tiny solids and liquid droplets are made up of hundreds of different chemicals and are so small that they are almost inevitably inhaled, according to the EPA. PM10 and PM2.5 are particles with diameters less than 10 microns and 2.5 microns respectively, which pose the greatest risk to human health because once inhaled, they can penetrate deep into the lungs and even enter the bloodstream, impairing the normal functions of the human body.
Air purifiers are supposed to help us improve indoor air quality by removing these types of particles from the air—but how effective are they? That’s where our CNET Labs team comes in. Return the air to a breathable condition.
To achieve this, we need to find a way to generate quantifiable and fairly repeatable particle counts; an environment or “test chamber” to house these particles and the air purifier unit; and an accurate particle counter that acts as our The control device allows us to visualize this data. Here are our thoughts:
Customized smoke bomb, made of 50% potassium nitrate (KNO3), 40% sucrose (sugar) and 10% sodium bicarbonate (baking soda), and equipped with a safety fuse for safe ignition from a distance. The sugar acts as our fuel source, while the potassium nitrate acts as the oxidizer, and the baking soda ensures that our dry mixture maintains a slow and even burn.
our Air purifier laboratory It was designed and built by Eric and myself. Its features include a clear-view front panel made of Plexiglas and a channel for gloved hands on the right side, which allows us to operate the air purifier, a particle counter holder for controlling the device, and two secure air and fumes inside A fan combustion chamber for proper mixing, vents to ensure there is always a small amount of fresh air, an ignition port to light the smoke grenade from outside the unit, and an exhaust port to safely remove the remaining smoke from the combustion chamber and building after burning is tested every time. The chamber is not airtight, but is tight enough to ensure that no dangerous amounts of smoke escape into the surrounding environment.
use Temptop PMD331 Particle Counter, we were able to verify that just 5 grams of smoke bomb dry mixture produces approximately 590 million to 610 million particles per cubic meter. The device counts particles of different sizes, including PM2.5 and PM10, and records this data every 15 seconds. While we can count particles of different sizes individually, we are concerned with the total number of particles; that is, the sum of all particles of different sizes.
With the essentials figured out, our test procedure is as follows: We turn on the particle counter and let it run continuously. We prepare a 5-gram smoke bomb and ignite it through the ignition port after installing the air purifier and ensuring a good seal. Once the indoor air reaches particle saturation (more than 580 million particles/cubic meter), we turn on the relevant air purifier. The data extracted from Temptop allows us to instantly and accurately track the impact of air purifiers on particle counts.
Under normal conditions, when there is no smoke in the test chamber, the total number of particles reported by Temptop is around the 10 million mark, so think of it as the “finish line” in this particle-removal race. In our testing logic, the faster an air purifier can bring particle counts back below 10 million particles per cubic meter, the better. We conduct this test twice with each air purifier, once at the lowest fan setting and once at the highest fan setting to visualize the operating range of each unit. Check out the results for each device we tested at low and high fan settings in the GIF below:
Noise level test
It’s a simple test, but it’s telling. We use a decibel meter to measure the loudness of the air purifier at low, medium, and high fan settings. This is especially important if you plan on installing an air purifier in your bedroom and letting it run all night long without disturbing your sleep.
We conduct this test in a sound enhancement studio to ensure that the decibel meter only picks up the sonic stimulus from the air purifier, excluding other possible sources. The lower the number, the quieter the air purifier operates. You can see the results for yourself in the image below; each device we tested produced about 35 decibels of noise at low settings, but we found a much bigger difference at medium and high settings.
Energy consumption
If you’re like me and allergies are your worst enemy, you’d prefer your air purifier to run all the time. The only worry is that your energy bills will definitely increase, but by how much?
To answer this question, we used a device called the Kill-a-Watt to measure the power each air purifier consumes at different fan settings. From there, we can correlate that to the average monthly cost of running the unit non-stop. All you need to know is the cost of energy per kilowatt hour in your state. The following formula best describes it:
Average cost to run an air purifier non-stop for a month = Watts consumed/1000 * 24 hours * 30 days * Average utility cost per kilowatt hour in your state.
The chart below shows how much each air purifier we tested cost to run for a full month in various states, with different energy efficiencies, and at high fan settings.
